1. Field of the Invention
The present invention relates, in general, to apparatus for measurement of forces and moments acting on rotatable members and specifically to a wheel load measurement system for measuring forces and moments acting upon vehicle wheels.
2. Description of the Related Art
Wheel load transducers are known for attachment to a vehicle wheel to measure moments and forces, including torque, applied to the wheel. Such a transducer is typically in the form of an annular member affixed at an outer peripheral portion to a rim adapter welded to the wheel rim. The rim adapter has a plurality of circumferentially spaced apertures aligning with corresponding apertures in the outer periphery of the transducer for receiving bolts therethrough to fix the transducer to the wheel rim. A hub adapter, which also has a plurality of circumferentially spaced apertures, is mountable to the inner annular portion of the transducer and fastened thereto. The hub adapter includes a standard hole arrangement for attachment to vehicle wheel bolt lugs.
A plurality of radially-extending webs or beams connect the inner and outer annular portions of the transducer. Moments and forces observed on the wheel are measured by sensors, such as strain gages, which are adhesively affixed to exterior surfaces of the webs-or beams. Certain of the strain gages provide force measurements, while others are positioned to provide torque, steering and camber moment measurements.
Some of these transducers, however, are unable to measure vertical and fore and aft forces. More recently, a combined transducer/hub adapter has been introduced for use with the conventional transducer. The transducer/hub adapter has an outer, radially outward extending flange, a generally circular inner wall, and a plurality of webs or beams interconnecting the outer flange and the inner wall. The beams are in the form of a thin, cross-sectional strip having a radially inner surface, a radially outer surface and opposed side edges or walls upon which sensors are mounted for measuring the vertical and fore and aft forces. Another recent effort to measure these forces uses the conventional transducer, but modifies the beam by forming instead a stem extending from the inner annular portion of the transducer and a perpendicular crossleg unitarily formed with the stem and connected to the outer peripheral portion of the transducer. Sensors are mounted in wells formed in each of the stem and the crossleg.
While these transducers successfully measure moments and forces observed on the wheel, all transducers exhibit some degree of imperfection known as crosstalk. Crosstalk is a measurement error that occurs when forces or moments are applied at in directions at right angles to the desired measurement direction. Further, these transducers are unable to measure the forces and moments exerted on each of two wheels in a dual wheel mount.
Thus, there is desire to develop transducers that can also be used to provide forces and moments measurements for dual wheel sensing. It is also desirable that the transducers minimize crosstalk.
The wheel load measurement system described minimizes the number of components needed to measure forces and moments respectively experienced by one or more wheels while minimizing crosstalk. A first aspect of the system is mountable upon a wheel rim supporting a wheel. The wheel rim is rotatable about an axis of rotation. The system includes a sensor body including an inboard ring connectable to the wheel rim, an outboard ring connectable to a hub adapter, the outboard ring axially-spaced from the inboard ring, and a plurality of beams extending between the inboard ring and the outboard ring. The system also includes a plurality of sensors, each of the plurality of sensors fixed to an external surface of one of the plurality of beams. The plurality of sensors is operable to provide a signal indicating at least one of three principal forces and three principal moments experienced by the sensor body.
Another aspect of the system measures forces and moments on respective wheels of a dual wheel pair. This dual wheel load measurement system is mountable upon an inboard wheel rim supporting an inboard wheel of a dual wheel pair and an outboard wheel rim supporting an outboard wheel of the dual wheel pair. The inboard wheel rim and outboard wheel rim are rotatable about a common axis of rotation. The system includes a first sensor body including a first inboard ring connectable to the inboard wheel rim, a first outboard ring connectable to a hub adapter, the first outboard ring axially-spaced from the first inboard ring, and a first plurality of beams extending between the first inboard ring and the first outboard ring. The system also includes a first plurality of sensors, each of the first plurality of sensors fixed to an external surface of one of the first plurality of beams. The first plurality of sensors is operable to provide a signal indicating at least one of three principal forces and three principal moments experienced by the first sensor body.
The dual wheel load measurement system includes a second sensor body axially adjacent to the first sensor body. The second sensor body includes a second inboard ring connectable to the outboard wheel rim and identical to the first inboard ring, a second outboard ring connectable to the hub adapter, the second outboard ring identical to the first outboard ring and axially-spaced from the second inboard ring, and a second plurality of beams extending between the second inboard ring and the second outboard ring. A second plurality of sensors is operable to provide a signal indicating at least one of three principal forces and three principal moments experienced by the second sensor body. Each of the second plurality of sensors fixed to an external surface of one of the second plurality of beams.
Other features of the system are contemplated and are described herein in detail.